Compare ways to improve VO₂Max

There is more than one way to improve VO₂Max. Here we compare four approaches studied in research, looking at what participants did and how their values changed. The figures in the table are averages for those study participants. Results from studies with different participants or durations cannot be directly ranked by effectiveness or used to predict your own results.

What reviews of the research tell us

• Both continuous exercise and HIIT have been reported to improve VO₂Max. A review of 28 controlled trials in healthy adults aged 18–45 found increases of 4.9 mL/kg/min with continuous exercise and 5.5 with HIIT versus no exercise. The estimated difference between HIIT and continuous exercise was 1.2 mL/kg/min, described as small (Milanović et al., 2015).
• The size of the improvement varies between studies. In the same review, studies including people with lower initial fitness and studies with longer interventions tended to show greater improvements. This does not predict an individual's change.
• Interval length alone does not determine which method is better. A review of 53 randomized controlled trials (1,514 participants) in adults without disease found improvements with short HIIT intervals compared with no exercise. Advantages over moderate continuous exercise appeared in categories such as long intervals and high exercise volume, but results differed between populations. Interval length, exercise volume and intervention duration were classified separately; the review did not establish an optimal combination for everyone (Wen et al., 2019).
• Some studies matching total work found larger improvements with HIIT. In physically active young men, both 4 × 4-minute and 15/15-second intervals produced larger VO₂Max increases than continuous running. However, the difference between the two interval groups was not significant (Helgerud et al., 2007). This alone does not show that long intervals are optimal regardless of age or health.
• Interval walking improved fitness in a trial in middle-aged and older adults. Alternating 3 minutes of brisk and 3 minutes of slow walking improved cardiorespiratory fitness more than continuous moderate walking in this population (Nemoto et al., 2007).

Choosing an approach that suits you

• You do not exercise regularly → Start with a sustainable activity such as walking, at low intensity for short periods. See how to start continuous exercise, and increase gradually according to how you feel (MHLW, 2023).
• You already walk regularly → Read the interval-walking research and precautions. You do not need to reproduce the study duration or intensity from the outset.
• You are interested in HIIT → Read about the study participants, intensities and limitations and the checks before starting. First consider whether it suits your fitness and health.
• You have little time → Consider the time you can set aside for recovery, warm-up and cool-down as well as work intervals. Short intervals do not necessarily mean an easier session.
• You have a medical condition or take medication → Consult your doctor first. If your medication affects heart rate, heart rate is not a suitable guide to intensity.

Do not force yourself to increase intensity or volume to chase a research average. See How VO₂Max is measured for the limitations of each measurement method.